Method of reclaiming wool



Patented Mar. 10, 1942 METHOD OF RECLAIMING WOOL Carl S. Ferguson,NewtomMass.

No Drawing. Application April 3, 1939, Serial No. 265,768

7 Claims.

This invention relates to a method of reclaiming wool fibers bychemically destroying fibers of natural silk, cellulose acetate, rayon,cotton and other vegetable matter which may be mixed with wool, suchremoval being accomplished with no more deleterious effect on the woolfibers than results from the usual acid carbonizing treatment now ingeneral use for destroying cotton and other vegetable matter mixed withwool.

In my co-pending application Serial N 0. 85,701, filed June 17, 1936,pursuant to which application Letters Patent of the United States No.2,152,640 were granted to me on April 4, 1939, there is described amethod of treating wool and silk mixtures for the removal of silktherefrom by immersing the fibers in a concentrated solution of zinc andcalcium chlorides in stated proportions and at given temperatures, suchtreatment also resulting in the conditioning of any cellulose acetatefibers which may be present so that subsequent baking such as is done inthe ordinary carbonizing processes will disintegrate the celluloseacetate fiber and permit its ready removal as dust.

According to the present invention, a small amount of aluminum chlorideis added to the zinc-calcium chloride solution described in saidapplication, and the resulting solution is used in the treatment of woolmixtures which may contain not only natural silk and cellulose acetate,but also cotton, rayon, and other vegetable matter such as burrs, bitsof grass, wood and'the like. Suitable treatment in such a solution notonly dissolves out the silk and conditions the cellulose acetate forbaking, but also softens the vegetable matter and saturates the samewith chemicals which causes the destruction of such matter whensubsequently baked. Since the zinc and calcium chlorides by themselvesare not effective in preparing vegetable matter for baking, and sincethe small amount of aluminum chloride used would be ineffective for suchpurpose, it is believed that the aluminum chloride has a sort of triggeraction in the solution and activates either the zinc chloride or calciumchloride, or both, so that their presence together in the vegetablematter during baking results in the destruction of such matter. Thus, asingle liquid treatment, followed by drying and baking, will remove fromwool mixtures any natural silk, cellulose acetate, rayon, cotton orother vegetable matter which maybe present, with practically nodeterioration of the wool itself, that is, no more than inevitablyresults from the customary carbonizing treatment generally employed forthe removal of vegetable matter. 7

For practicing the invention, a suitable solution should be prepared bydissolving sufficient quantities of the chlorides of zinc, calcium andaluminum to make a concentrated solution having density of from 50 to 55B. at room temperature. The salts may be introduced in any desiredorder, or all together. Considerable latitude in the ratio between thequantities of the individual salts in the solution is permissible, butthere must be considerably less of the aluminum chloride present than ofeither of the other two chlorides. For best results, the ratio betweenthe zinc chloride and calcium chloride should be between 7:3 and 3:7,sufiicient aluminum chloride being added to make 3% to 6% in the finalsolution. o.

The following specific solution is recommended, but it is to beunderstood that the quantities and proportions of ingredients given areby way of example only and not limitation. To each 7 gallon of water addeleven pounds of calcium chloride, seven pounds ofzinc chloride, and onepound of aluminum chloride, and. dissolve. The resulting solution willhave a boiling point of 255 to 260 F. and a density of about 52 B. at F.This solution is heated to a temperature of from to 230 F., the rapidityof the action of the solution in dissolving silk depending on itstemperature. About 215 F. is optimum. The fibers to be treated are thenimmersed in the hot solution and are agitated therein until the naturalsilk fibers are completely dissolved. This will ordinarily require fromeight to fifteen minutes at temperatures within the range stated. Thefibers may be in the form of piece goods, rags, clippings, picked stock,thread waste, or any other form sufficiently open and loose to permitfree penetration and circulation of the solution. Since the stockwhenintroduced into the bath is ordinarily at room temperatures, it willtend to cool the bath somewhat. For this reason it is preferable toapply heat to the solution when a batch of stockis introduced, so as tomaintain the temperature close to the optimum. For the same reason also,agitation is important to prevent local cooling of the solution whichpenetrates to the interior of a mass of stock below the efiective rangeof temperature, thus leaving a portion of the stock in-adequatelytreated. While immersion of the stock during the liquid treatment ispreferred as a simple effective method, it is to be understood that theinvention includes other equivalent methods of liquid treatment such asspraying, or dipping the stock and suspending it in a heated atmosphere.

After the liquid treatment has been completed, the liquor ismechanically extracted as thoroughly as possible from the stock bysqueeze rolls, centrifuges or other means which maintain theconcentration of the recovered liquor. The stock is then dried, thisstep being hastened by any convenient drying apparatus in which thestock may be exposed to a current of air at a temperature of 180 to 190F. The dried stock is then baked at a temperature of from 220 to 240 F.for a period of about to minutes or until the vegetable content of thestock has been destroyed and is ready to be dusted out. The resultingstock is free of natural silk, cellulose acetate, rayon, cotton, andother vegetable matter.

The stock is then thoroughly washed to remove the residual salts on thefibers from the liquor carried out from the treating bath. To this endfive or six changes of water are employed, the first wash water beingpreferably slightly acidified with hydrochloric or acetic acid, andmoderately hot. The washing is followed by a final drying.

The three chlorides employed in the solution are believed to function asfollows. The zinc chloride is the active agent which dissolves the silkand conditions the cellulose acetate. The calcium chloride acts as apalliative to protect the wool fibers from being injured by the zincchloride. As far as can be determined, these two chlorides have noappreciable effect on vegetable matter, either singly or together.Aluminum chloride in proper concentration on vegetable fibers appears toundergo a partial hydrolysis with the liberation of hydrochloric acidgas which can be amployed to attack the vegetable fibers anddisintegrate them. A 3% to 6% solution of aluminum chloride, however,would be ineffective by itself as a carbonizing agent for vegetablematter. In the presence of larger quantities of zinc chloride andcalcium chloride, however, the aluminum chloride appears to activate'oneor both of the other chlorides so that they together function as anefilcient carbonizing agent.

I claim:

1. A method of removing natural silk and vegetable matter from a mixturecontaining wool, natural silk and vegetable matter, comprising treatingthe mixture with a hot concentrated solution of zinc chloride, calciumchloride and aluminum chloride to dissolve the silk, the zinc andcalcium chlorides being in excess of the aluminum chloride, removingexcess solution after treatment, drying and baking the mixture todisintegrate the vegetable matter, and washing the residue.

2. A method of removing natural silk and vegetable fibers from a mixturecontaining wool, natural silk and vegetable: fibers, comprising treatingthe mixed fibers with a hot concentrated solution of zinc, calcium andaluminum chlorides to dissolve the silk, the calcium chloride being inexcess of the zinc chloride, and the calcium and zinc chlorides bothbeing greatly in excess of the aluminum chloride, mechanicallyextracting excess solution from the fibers after treatment, drying thefibers, baking the dried fibers to disintegrate the vegetable matter inthe mixture, washing the residual fibers, and drying the washed fibers.

3. A method of removing natural silk and vegetable fibers from a mixturecontaining wool, natural silk and vegetable fibers, comprising treatingthe mixed fibers with a hot concentrated solution of zinc chloride andcalcium chloride containing 3% to 6% aluminum chloride to dissolve thesilk, mechanically extracting excess solution from the fibers aftertreatment, drying the fibers, baking the dried fibers at a temperaturebetween 220 to 240 F., whereby the vegetable matter therein isdisintegrated, washing the residual fibers in water, and drying thewashed fibers.

4. A method of reclaiming wool fibers from mixtures containing wool,natural silk and vegetable matter, comprising immersing the mixture in abath of concentrated solution of zinc, calcium and aluminum chlorides inthe approximate ratio of 'l :11:1 while maintaining the bath at atemperature between and 230 F., mechanically extracting excess solutionfrom the residual fiber mixture after the natural silk has dissolved,drying and baking the fibers at temperatures between 220 and 240 F. todisintegrate the vegetable matter, and Washing and drying the residue.

5. A method of reclaiming wool fibers from mixtures containing wool andcellulose acetate fibers, which comprises treating the mixed fibers witha hot solution of zinc, calcium and aluminum chlorides, the zinc andcalcium chlorides being greatly in excess of the aluminum chloride,removing excess solution from the fibers, drying the fibers, baking thedried fibers at a temperature of from 220 to 240 F., and washing theresidue.

6. A method of reclaiming wool fibers from mixtures containing wool andcellulose acetate fibers, which comprises treating the mixed fibers witha hot solution of zinc chloride, calcium chloride and aluminum chloridein the approximate ratio of '7:11:1, removing excess solution aftertreatment, drying, baking the dried fibers at a temperature between 220and 240 F., and washing the residue.

7. A method of reclaiming wool fibers from mixtures containing wool,natural silk and cellulose acetate fibers, which comprises treating themixed fibers with a solution of zinc chloride, calcium chloride andaluminum chloride in the approximate ratio of '7:ll:1, the temperatureof the solution being near but below its boiling point, removing excesssolution from the fibers after treatment, drying the fibers, baking thedried fibers at a temperature between 220 and 240 F., and washing theresidue. v

CARL S. FERGUSON.

